It is often desirable to know information about fluid levels in reservoirs. Determining fluid levels and controlling fluid levels in reservoirs, such as in sewage tanks, wells, water cisterns or tanks, and other fluid system and storage vessels, whether enclosed or open and exposed to the environment, has been done in a number of ways. For example, in tanks that are visually accessible, an operator may periodically take visual readings of the fluid level.
Visual readings, however, are often not desirable in systems where an automatic response is required when the fluid level reaches a certain threshold. In such cases the activation of a pump or valve may be necessary to move more fluid into the tanks or to discharge fluid from the tank. In systems where visual readings are not available or when an immediate response is required, control systems are typically employed that are responsive to a fluid level indication. Such control systems may illuminate a light on an indicator panel representing the fluid level and/or trip an audible alarm to notify a human operator that corrective action is required.
Examples of fluid level sensing devices for use with wastewater reservoirs or other fluid holding vessels are discussed in U.S. Pat. No. 6,595,041 of Jul. 22, 2003 and U.S. Pat. No. 6,443,005 of Sep. 3, 2002 which are both incorporated by reference herein.
Different types or configurations of tanks often require different types or configurations for control systems associated with the tank. For example, some tanks may have one pump while other tanks have more than one pump which are capable of moving fluids out of the tank. In addition, some tanks may include fluid level sensing devices in the form of mechanical floats positioned at various levels in the tank, while other tanks may use fluid level sensing devices such as a pressure bell located at the bottom of the tank such as shown in U.S. Pat. No. 6,595,041.
Although control systems have been produced for each of these systems, such systems are generally limited to working with only a specific type of wastewater tank configuration. If the requirements for the tank change over time, a completely new system which can accommodate the new requirements for the tank must be installed. Thus there exists a need for a control system which is more easily adaptable to changing requirements for a wastewater system.
Wastewater control systems are often designed to cause one or more pumps to start pumping fluid out of a tank responsive to the level of fluid in the tank. It is often desirable to use pumps with single phase motors for this purpose. Because single phase motors do not have multiple phases, to begin rotation, start windings are required to achieve motor acceleration. Historically, this has been achieved with the use of a potential relay that measures the voltage during the start. In response to the voltage measurement, a relay can be configured to drop out the start winding. Because start capacitors operate in parallel with the start winding, the relay must open at the correct time so that the voltage does not build too high and blow up the start capacitor. Thus, to increase the reliability of such control systems, there exists a need for a control system which can reliably prevent start capacitors from being damaged.
Embodiments of control systems for monitoring and controlling wastewater systems may include a momentary contact push button accessible from the outside of the control system housing. Such a push button may be capable of temporarily silencing an alarm produced by the control system until the wastewater system is again working properly. For example, the control system may include a circuit board within the housing of the control system which is operative to monitor and control conditions associated with a wastewater system. The circuit may include a latching relay which is coupled to the push button. The latch relay may be responsive to the momentary contact push button being pressed to open (i.e., deactivate) the portion of the circuit which produces the alarm.
The momentary contact push button may be positioned on the control system to be accessible by an operator without opening the housing. However, control system housings are often designed to comply with one or more standards for water resistance such as the National Electrical Manufacturers Association (NEMA) standards. An example of such a standard may included a NEMA 4X standard for a housing which specifies that the housing is capable of resisting certain levels of water and corrosive materials. In a wastewater environment, the control panel may be relatively close to the fluids that are being monitored and controlled by the control panel. In addition, in a wastewater environment, the housing for the control system may be exposed to relatively high levels of water vapor, humidity, or other potentially corrosive and destructive gases and fluids. Thus, the circuits within the housing of the control system must be protected from the environment outside the housing.
Placing holes through the walls of such housings for placement of push button silencing alarms can compromise the NEMA rating of the housing. Although gaskets with oiltight push button switches can be used, adapting a housing to include such a button without compromising the NEMA rating of the housing can add to the complexity and cost of the manufacture of the control system. As a result, there exists a need for an improved housing for wastewater control panels which enables alarms to be silenced without opening the housing and which is adapted to minimize the opportunity for environmental conditions outside the housing from degrading the circuits and other components inside the housing.